diff --git a/GSM/GSMCommon.cpp b/GSM/GSMCommon.cpp
index 711ca70..5e9e4ae 100644
--- a/GSM/GSMCommon.cpp
+++ b/GSM/GSMCommon.cpp
@@ -2,6 +2,8 @@
 * Copyright 2008 Free Software Foundation, Inc.
 * Copyright 2011 Range Networks, Inc.
 *
+* SPDX-License-Identifier: AGPL-3.0+
+*
 * This software is distributed under the terms of the GNU Affero Public License.
 * See the COPYING file in the main directory for details.
 *